The total amount of wood that you need to buy is: 30¹/₂ inches
How to find the Perimeter of a rectangle?
The formula for the perimeter of a rectangle is:
P = 2(L + W)
Where:
L s Length
W is Width
Now, we are told that the frame has the dimensions as:
Length = 8³/₄ inches = ³⁵/₄ inches
Width = 6¹/₂ inches = ¹³/₂ inches
Thus:
P = 2(³⁵/₄ + ¹³/₂)
P = 2(³⁵/₄) + 2(¹³/₂)
P = ³⁵/₂ + 13
P = 61/2
P = 30¹/₂ inches